1. Field of the Invention
The invention relates to a video signal amplifier arrangment for a television display tube, comprising an amplifier transistor whose collector is coupled to a terminal of a load impedance, the other terminal of which is coupled to a power supply source, the output signal of the amplifier being taken from said collector which is coupled to a video control electrode of the display tube.
Such amplifier arrangements present the following problem: a low load impedance of the amplifier transistor will contribute to a considerable current in the transistor with a large power dissipation. If this load impedance has a high value, the amplifier will have an insufficient passband.
2. Description of the Related Art
This problem can be solved by substituting the load for an active element, for example a second amplifier transistor having a polarity which is opposed to that of the first. Such a solution using two complementary push-pull cascode arrangements is described, for example in the documents U.S. Pat. Nos. 4,727,336, and 4,035,840 or JP-A-63 26105.
Nevertheless, such a solution makes it difficult to realize the drive of the second amplifier transistor, because the use of a connection capacitance (documents U.S. Pat. No. 4,035,840 and JP-A-63 26105) necessitates a compromise as regards the transition frequency of the capacitive connection, and a drive transmitting the dc component will complicate the realization because of the dc offset between the bases of the two transistors (for example, the circuit described in document U.S. Pat. No. 4,727,336 has two power supplies for this reason: +55 V and -55 V).